1. Field of the Invention
The present invention relates to a showerhead for film-depositing vacuum equipment and, more particularly, to a showerhead for film-depositing vacuum equipment, which uniformly and stably supplies a process gas onto a substrate during a film deposition process, such as chemical vapor deposition, thereby improving the quality of the formed film and preventing the undesired deposition of particles.
2. Description of the Prior Art
In response to the ongoing high-integration of semiconductor devices, the need becomes stronger to control process parameters more precisely in fabrications of semiconductor devices including a film deposition process. Many efforts are done to achieve process reliability amongst and within substrates.
In particular, studies are underway to improve process reliability in an equipment that adopts a showerhead for supplying a process gas during chemical vapor deposition in which a film is deposited on a substrate by a surface chemical reaction. Recently, an attempt to make an easy adjustment of components in films by controlling the injection velocity of reactive gasses was introduced in Korean Patent No. KR 100849929 (Korean Publication No. KR 20080025277) (hereinafter, referred to as Cited Document 1).
Referring to Cited Document 1, a reactive gas and an injection support gas are mixed inside a showerhead and are injected onto a substrate. In addition, it is possible to minimize backward diffusion of the reactive gas towards the showerhead and unwanted deposition of particles resulting from the reaction of reactive gas and/or byproduct gasses on the bottom of the showerhead, which becomes enabled by separately injecting a purge gas towards the substrate. In addition, it is also possible to suppress ring-shaped contamination on the exit end of the reactive gas injection tubes by injecting the purge gas while surrounding the exit end of the reactive gas injection tube.
Here, the reactive gas refers to a source gas, which contains a component of a film to be deposited. The injection support gas refers to a kind of gas that is used to adjust the injection velocity of the reactive gas by being mixed with the reactive gas at inside of the showerhead, which generally includes inert gases that are unlikely to undergo a chemical reaction with the reactive gas. In addition, the purge gas refers to a gas that is used to adjust the total flow rate and to prevent bottom surface of the showerhead from being contaminated. The purge gas is not necessarily limited to an inert gas and may be another kind of gas. Examples of the purge gas are Ar, N2, O2, He, H2, NH3, AsH3, PH3, or the like, and they may include a chemical component of a film to be deposited, but rarely do they decompose or leave behind a deposition inside the showerhead.
The purge gas needs to be very uniformly injected. Otherwise, it may result in unintended particle deposition on some portion of the showerhead and cause a non-uniformity of deposition. Therefore, it is very important to uniformly inject the purge gas.
FIG. 1 shows the configuration of a showerhead disclosed in Cited Document 1. As shown in the figure, two reactive gas showerhead modules 110 and 120, one purge gas showerhead module 130 and a cooling jacket 140 are sequentially stacked from top to bottom. FIG. 2 shows a detailed view of the vicinity of guide tubes 131 and 141 through which reactive gas injection tubes 111 extended from the reactive gas showerhead module 110 pass through the cooling jacket 140. As shown in the figure, if there is substantially no space between the purge gas showerhead module 130 and the cooling jacket 140, it is difficult to uniformly distribute the purge gas to the guide tubes 141 and 142 by merely aligning a purge gas injection hole 132 or a purge gas outlet 133 with guide tubes 142 or 141 mounted at the cooling jacket 140, respectively.
In order to solve above problem, Korean Patent Application Publication No. 10-2007-0112354 (hereinafter, referred to as Cited Document 2) proposed a purge gas redistribution space 143 having a predetermined thickness, indicated by “h,” between the purge gas showerhead module 130 and the cooling jacket 140, as shown in FIG. 3 and FIG. 4. However, according to Cited Document 2, the length (l1 in FIG. 3) of the reactive gas injection tubes 111 and 121, which are connected to the bottoms of the reactive gas showerhead modules 110 and 120, must be longer than the height (Δl in FIG. 3) of the purge gas showerhead module 130. As several reactive gas showerhead modules 110 and 120 are sequentially stacked on the purge gas showerhead module 130, the length of the reactive gas injection tubes 111 and 121 which are connected to the bottom of the reactive gas showerhead modules 110 and 120, increases further.
The presence of Δl that has to be basically included may cause drawbacks, such as warping in the tubes or difficulty in assembling during fabrication processes or maintenances of the showerhead. As the length of the reactive gas injection tubes 111 and 121 is increased, a problem of traveling a longer distance from the reactive gas showerhead modules 110 and 120 to the bottom of the cooling jacket 140 may result. In an example, a large pressure drop may make it difficult to efficiently supply the reactive gas to the substrate. In addition, when depositing several layers of a film, a reactive gas during the former step may reside inside the showerhead at the next step.
In addition, in conventional film-depositing vacuum equipments, in case that the kind of the reactive gas being introduced into a reaction chamber (not shown) is to be changed, it is usually done by the manipulation of valves. That is, a switching method has been used. However, there is a possibility that the changed process gas may flow back towards the former process gas line. As long as different kinds of process gases are commonly used in one process gas supply tube, the problem of contamination still exists. Therefore, it is preferable that a dedicated process gas supply line is used for one kind of process gas.
When process gases having different properties are mixed inside the showerhead that serves to uniformly inject the process gases onto the substrate, for example, when a Tri-Methyl Gallium (TMG) process gas is used as a source of Ga and an NH3 process gas is used as a source of N and these are mixed together inside the showerhead in the process of depositing a GaN film for an LED by MOCVD, an unintended gas reaction may occur inside the showerhead, thereby forming particles.
Therefore, in such a case, a post-mixing method is generally used; i.e. different process gases pass through the showerhead without being mixed together, but are mixed together between the showerhead and the substrate.
FIG. 1 showing the configuration of Cited Document 1 illustrates a related technology. That is, a first reactive gas that has been introduced to the inside of the reactive gas showerhead module 110 through an inlet 112 is mixed with an injection support gas that has been introduced to the inside through another inlet 113 in order to regulate the injection velocity of the reactive gas. The mixed gas passes through guide tubes 122 along the inside of the reactive gas injection tubes 111, thereby passing through the inside of the reactive gas showerhead module 120 below. The first mixed gas, without being mixed with the second reactive gas within the showerhead, is then injected towards the substrate (not shown) placed inside the reaction chamber.
In this configuration, however, an increase in the number of reactive gases which constitute the elements of the film may result in the showerhead of a complicated structure. FIG. 1 shows that the two reactive gas showerhead modules 110 and 120 are stacked in the vertical direction. However, continuously increasing the number of the reactive gas showerhead modules in response to an increase in kinds of the reactive gases may cause a problem due to the limited space allocated to the inside of the reaction chamber.